Wall shear stress in Görtler vortex boundary layer flow

2009 ◽  
Vol 21 (8) ◽  
pp. 084106 ◽  
Author(s):  
Tandiono ◽  
S. H. Winoto ◽  
D. A. Shah
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Boundary Layer Flow ◽  
Wall Shear ◽  
Layer Flow

Laminar boundary-layer flow past a two-dimensional slot

1977 ◽  
Vol 83 (1) ◽  
pp. 33-47 ◽  
Author(s):  
Ian J. Sobey
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Stress Level ◽  
Boundary Layer Flow ◽  
Downstream Side ◽  
Flow Past ◽  
Shear Stress Level ◽  
Wall Shear ◽  
Layer Flow

Observations by Cornhill ' Roach (1976) of sudanophilic lesions in the vicinity of intercostal arteries in rabbit aortas have shown that lesions develop on the downstream side of the associated ostia. There is considerable conjecture as to the role which varying levels of wall shear stress play in the development of such lesions; Cornhill ' Roach implicate high wall shear stress levels. We develop a consistent model of steady boundary-layer flow past a side slot assuming that there is Stokes flow in the side slot and that the main body of the boundary layer remains undisturbed. Our results show that increased levels of wall shear stress occur both upstream and downstream of the slot. If the withdrawal of fluid through the side slot is sufficiently great there may be a stagnation point on the downstream side of the slot. The wall shear stress level near the slot depends on both normal and transverse motions at the mouth of the slot. Indeed, very near the slot, on a length scale comparable with the slot width, the wall shear stress level depends only on the transverse motions at the mouth of the slot.

Wall shear stress caused by small amplitude perturbations of turbulent boundary-layer flow: an experimental investigation

1977 ◽  
Vol 83 (3) ◽  
pp. 433-464 ◽  
Author(s):  
D. Ronneberger ◽  
C. D. Ahrens
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Turbulent Boundary Layer ◽  
Shear Wave ◽  
Sound Wave ◽  
Viscous Sublayer ◽  
Turbulent Boundary Layer Flow ◽  
Wall Shear ◽  
Layer Flow

The oscillation of the wall shear stress caused by imposing sound on a turbulent boundary-layer flow constitutes a boundary condition for the solution of the acoustic wave equation. The no-slip condition at the wall requires the excitation of a shear wave which is superimposed on the sound wave. The shear wave propagates into the turbulent medium. The wall impedance (shear stress/velocity) of streamwise polarized shear waves has been measured in two different ways, namely (a) by evaluating the phase velocity and the attenuation of a plane sound, wave which propagates in turbulent pipe flow, and (b) by evaluating the resonance frequency and the quality factor of a longitudinally vibrating glass pipe which carries turbulent flow. The results, which were obtained over a wide range of Strouhal numbers, exhibit very good agreement between the two measuring methods. The wall shear stress impedance is strongly affected by the turbulence. This indicates that the turbulent shear stress is modulated by the shear wave. At all measuring conditions, the propagation of the shear wave was confined essentially to the inner portion of the turbulent boundary layer. In principle, two different Strouhal numbers, based on inner and outer variables respectively, describe the dynamics of the Reynolds stress, even in the inner layer (Laufer & Badri Narayanan 1971). However, it turns out that the outer Strouhal number (based on the diameter and the centre-line velocity) has no noticeable effect on the wall shear stress impedance. The dependence of the impedance on the inner Strouhal number (based on the friction velocity and the viscosity) reveals that the shear wave is strongly reflected at the edge of the viscous sublayer. It is concluded that the stress-to-strain ratio at the edge of the viscous sublayer corresponds either to a viscoelastic medium or even to a medium with negative viscosity.

Preston Tube Calibrations and Direct Force Floating Element Measurements in a Two-Dimensional Turbulent Boundary Layer

1982 ◽  
Vol 104 (2) ◽  
pp. 156-160 ◽  
Author(s):  
J. E. McAllister ◽  
F. J. Pierce ◽  
M. H. Tennant
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Turbulent Boundary Layer ◽  
Calibration Data ◽  
Two Dimensional ◽  
Force Measurements ◽  
Wall Shear ◽  
Layer Flow ◽  
Calibration Equations

Preston tubes provide a convenient means of estimating local wall shear stress. Practical difficulties arise from a lack of calibration data obtained in turbulent boundary layer flows and from the wide choice of calibration equations available mainly from pipe flow calibrations. The results of an experimental study comparing a large number of direct force local wall shear stress measurements in a near-zero pressure gradient two-dimensional turbulent boundary layer flow are presented. The results indicate that there is consistent and excellent agreement between the Patel intermediate calibration formula and the direct force measurements. Typical differences among the direct force measurements and several other proposed calibration equations are also shown.

On the Effects of a Flexible Structure on Boundary Layer Stability and Transition

2011 ◽  
Vol 133 (7) ◽  
Author(s):  
Ashraf Al Musleh ◽  
Abdelkader Frendi
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Young Modulus ◽  
Boundary Layer Transition ◽  
Beam Equation ◽  
Flexible Structure ◽  
Boundary Layer Stability ◽  
Wall Shear ◽  
Fluid Wall Shear Stress

Delaying the onset of boundary layer transition has become a major research area in the last few years. This delay can be achieved by either active or passive control techniques. In the present paper, the effects of flexible or compliant structures on boundary layer stability and transition is studied. The Orr-Sommerfeld equation coupled to a beam equation representing the flexible structure is solved for a Blasius type boundary layer. A parametric study consisting of the beam thickness and material properties is carried out. In addition, the effect of fluid wall shear stress on boundary layer stability is analyzed. It is found that high density and high Young modulus materials behave like rigid structures and therefore do not alter the stability characteristic of the boundary layer. Whereas low density and low Young modulus materials are found to stabilize the boundary layer. High values of fluid wall shear stress are found to destabilize the boundary layer. Our results are in good agreement with those published in the literature.

A Superposition Analysis of the Turbulent Boundary Layer in an Adverse Pressure Gradient

1951 ◽  
Vol 18 (1) ◽  
pp. 95-100
Author(s):  
Donald Ross ◽  
J. M. Robertson
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Turbulent Boundary Layer ◽  
Velocity Profile ◽  
Pressure Gradient ◽  
Adverse Pressure Gradient ◽  
Pressure Recovery ◽  
Stress Coefficient ◽  
Wall Shear

Abstract As an interim solution to the problem of the turbulent boundary layer in an adverse pressure gradient, a super-position method of analysis has been developed. In this method, the velocity profile is considered to be the result of two effects: the wall shear stress and the pressure recovery. These are superimposed, yielding an expression for the velocity profiles which approximate measured distributions. The theory also leads to a more reasonable expression for the wall shear-stress coefficient.

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